Tube forming means and method



Nov. 28, 1967 D. 1.. LOMBARD 3,354,681

TUBE FORMING MEANS AND METHOD Filed Dec. 28, 1964 4 Sheets-Sheet 1 //V VE/V 70A.

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United States Patent 3,354,681 TUBE FURMlN G MEANS AND METHOD Daniel L. Lombard, Youngstown, Ohio, assiguor to Lombard Corporation, Youngstown, Uhio, a corporation of ()hio Filed Dec. 28, 1964, Ser. No. 421,569 13 Claims. (til. 72-166) ABSTRACT 0F THE DISCLOSURE This patent discloses a method and apparatus for forming tubular members into elbow-shaped members with the use of a tapered land that provides a drag which varies from a minimum value at a first point on the circumference of said tubular member to a maximum value at a second point on the circumference of the tubular member, the arc length of the elbow-shaped member being determined by the initial length of the tubular member.

This invention relates generally to tube forming, and more particularly to a novel and improved means and method for extruding cold, pierced, metal billets into elbows and the like of desired curvature.

Various methods are presently employed for producing elbows of various curvatures. For example, one common method employs tubular material whose inside diameter is less than that required of the finished elbow product. The tubular material is heated to between 800 F. and 1000 F. The heated tubular material then is forced over an internal mandrel. The mandrel is both tapered and curved so that as the heated tubular material is forced thereover it is expanded to the desired inside diameter as well as being radiused, i.e., given the desired curvature.

It is important to note that in the above-described method of forming elbows: (1) the heating-of the undersized tubular material is a factor in the overall production cost of the elbow; (2) the heating of the undersized tubular material necessitates subsequent treatment of the formed elbow to induce therein the desired physical properties; (3) the surface defects initially present in the undersized tubular material are more pronounced after expansion and curving of the material whereby the formed elbow must be subjected to a surface finishing process or be rejected as a substandard product; and (4) the production rate of this process is relatively slow.

The principal objects of the present invention include:

To provide a novel and improved apparatus for bending tubular material into elbows of desired curvature and are lengths;

To provide apparatus for bending tubular material into elbows wherein the tubular material is at a relatively low temperature rather than being at a relatively high temperature as in conventional elbow forming processes;

To provide compact apparatus for individually extruding cold pierced billets sequentially into a tubular member and then into a finished elbow member;

To provide apparatus for transforming cold pierced billets into elbow members, the operation of said apparatus being substantially continuous whereby billets are introduced individually into one end of the apparatus and finished elbows are discharged from the exit end of the apparatus;

3,354,681 Patented Nov. 28, 1967 To provide apparatus for forming elbows Which are ready for use and do not require further processing; and

To provide a novel and improved method for forming elbow members. 4

In accordance with one embodiment of the present invention, apparatus is provided comprising a support block including an opening adapted to receive a cold tubular segment and within which said tubular segment is supported. Die means is provided at the lower end of the support block within the opening. The cold tubular segment is forced through the die means during which the tubular segment is caused to bend along a desired radius so as to form, for example, a welding elbow. The present die means is of the type which subjects the tubular segment during passage therethrough, to a frictional drag which varies substantially uniformly from a maximum value at one point on the circumference of the tubular segment to a minimum value at a diametrically opposite point on the circumference of the tubular segment. At the point of maximum frictional drag, the tubular segment will be forced through the die means at a velocity which is less than the velocity at which the tubular member will flow through that point of minimum frictional drag. Hence, the tubular segment will bend about the point of maximum frictional drag along a desired radius.

It is normal to expect during bending of tubular seg ments in the above-described manner, that the wall in the larger radius region of the elbow will tend to thinout during bending and be less than desired; and that the wall in the smaller radius region of the elbow will tend to thicken during bending and be greater than desired. However, the present die means is such that the resulting elbow will have a substantially uniform wall thickness throughout all regions thereof.

At the exit of the die means, there is provided a forming guide means which is engaged by the bent portion of the tubular segment for guiding the same, to insure that it follows the desired radius. It is important to note that the tubular segments are cold rather than being heated to an elevated temperature prior to bending, as in conventional elbow forming processes. Hence, a cost saving is achieved in that no preheating of the tubular segments is required. Each of the tubular segments is cut to a predetermined length whereby the resulting elbow will be of a desired arc length. Hence, the initial length of the tubular segment determines whether the resulting elbow will be a 30, 45, or any desired arc length elbow.

The above-described elbow forming apparatus is such that it may be operated continually whereby tubular segments are sequentially introduced into one end thereof and formed elbow members are discharged from the exit end thereof.

The present invention also contemplates a provision of apparatus wherein the above-described bending die means is combined with an extruded die means. In this embodiment, a cold, pierced, metal billet is extruded through the extrusion die means to form a tubular segment which, in turn, is forced through the bending die means to form the desired elbow member. Each of the billets may be cut from mill, bar, stock. The billets are comprises a water insoluble metal soap. One suitable lubricant coating process will be described later in the specification.

The above-described tube forming and tube bending apparatus also is operated continually wherein cold, pierced billets are sequentially introduced at one end thereof and formed elbow members are discharged from its exit end.

The above and other objects and advantages of the present invention will become apparent from the following detailed description by reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view illustrating a tube bending apparatus employing the bending die means of the present invention;

FIG. 2 is a fragmentary cross-sectional view, on an enlarged scale and taken along the line 11-11 of FIG. 3, illustrating one embodiment of the present bending die means;

FIG. 3 is a cross-sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a fragmentary cross-sectional view taken along the line IVIV of FIG. 5, illustrating an alternative embodiment of the present bending die means;

FIG. 5 is a cross-sectional view taken along the line VV of FIG. 4;

FIG. 6 is a fragmentary cross-sectional view taken along the line VIVI of FIG. 7, illustrating a further alternative embodiment of the present bending die means;

FIG. 7 is a cross-sectional view taken along the line VIIVII of FIG. 6;

FIG. 8 is a cross-sectional view illustrating combined tube forming and tube bending apparatus for transforming pierced metal billets into finished elbow members;

FIG. 9 is a cross-sectional view of a billet used in the apparatus of FIG. 8, having a lubricant coating applied to the surfaces thereof; and

FIGS. 10A to 10F are views schematically illustrating the step-by-step operation of the combined tube forming and tube bending apparatus of the present invention.

Referring now to FIG. 1, there is illustrated a tube bending apparatus comprising a support block 22 having an elongated bore 24 extending vertically therethrough. At the bottom of the support block 22 and residing within the elongated bore 24 there is provided bending die means 26, to be described in greater detail later in the specification, which serves to bend cold tubular segments along a desired radiusJAt the exit of the bending die means 26 there is provided forming guide means 28 comprising a block of steel 30 in which is formed an arcuate trough 32 whose. curvature corresponds to the desired curvature of the elbow member to be produced.

The tube bending apparatus 20 also includes a stem 34 which is supported for reciprocal movement into and out of the elongated bore 24. The stem operating means 36 is schematically illustrated in FIG. 1 and may comprise, for example, motor means 38 which is operatively connected to the stem 34 for forcibly displacing the same into the elongated bore 24 during formation of an elbow member and out of the elongated bore 24 at the completion of the formation of an elbow member. Motor means 38 includes conduits 4t), 42 both extending to four-way valve means 44 which is operated by solenoid means 46. Supply conduit 48 and return conduit 50 extend from the valve means 44 to a sump 52. In the conduit 48 there is provided a pump 54 for pressurizing the working fluid and communicating it to the motor means 38. The four-way valve means 44 has a stem lowering portion 56 and a stem raising portion 58. In FIG. 1, the stem lowering portion 56 is shown communicating with the conduits 40, 42 and the conduits 48, 50 whereby the stem 34 is forcibly lowered into the elongated bore 24. At the completion of an elbow forming operation, solenoid means 46 is activated to displace the stem raising portion 58 so as to communicate fluid through conduits 48, 42, to raise the stem 34 out of the elongated bore 24. It should be noted at this time, that the stem operating means 36 is intended merely to show one operable apparatus and that any other suitable means may be employed.

The tube bending apparatus 20 is adapted to contain two tubular segments during its operation. As can be seen in FIG. 1, a first tubular segment 60' has been forced through the bending die means 26 so as to form an elbow 62. Notice, however, that the first tubular segment 60 has not been forced completely through the bending die means 36 and that an unbent end portion 64 resides within the elongated bore 24. A second tubular member 66 is introduced into the elongated bore 24 and is lowered into engagement with the unbent end portion 64. The stem 34 has been lowered into engagement with the opposite end of the second tubular member 66.

Hence, as the stem 34 forces the second tubular segment 66 toward the bending die means 26, the first tubular segment 69 will be displaced completely through the bending die means 26 to complete the formation of the elbow 62. Thereafter, the second tubular segment 66 will be forced partially through the bending die means 26. At the limit of the stroke of the stem 34, the second tubular member 66 will be disposed in the position now occupied by the first tubular member 60 illustrated in FIG. 1.

It should be evident that the tube bending apparatus 20 may be operated continually wherein tubular segments are individually introduced into the elongated bore 24, the stem 34 is activated in a downward direction, and formed elbow members are discharged from the forming guide means 28.

The tube bending apparatus 20 illustrated in FIG. 1 produces 90 elbows. The tubular segments are cut to a length whereby when bent by the bending die means 26, the resulting elbow will have a predetermined arcuate length, i.e., whose ends subtend the desired angle. It should be evident, then, that tubular segments which are shorter than the tubular segment 66 will produce elbows whose ends subtend an angle of less than 90, while tubular segments which are longer than the tubular segment 66 will produce elbows whose ends subtend an angle greater than 90". It should be obvious, that when elbows greater than 90 are to be produced, the arcuate trough 32 will have to be extended.

Bending die means 26 Reference is now directed to FIGS. 2 and 3 wherein one embodiment of the bending die means 26 is illustrated. The bending die means 26 comprises a tapered land 68 which in this embodiment is a surface in the form of a truncated oblique cone. The land 68 terminates at its lower end in a circular shoulder 72.

In FIG. 3, a vertical plane is illustrated by the dashdot line 74. The plane 74 corresponds to the plane in which the cross-sectional view of FIG. 2 is taken. The elongated bore 24 has a center or central axis indicated at 76. The circular shoulder 72 is offset with respect to the bore 24 and has its center at 78. Consequently, the land 68 includes a first point wherein a tubular segment will be subjected to a maximum drag; and a second point 82, diametrically opposite to the first point 80, wherein a tubular segment will be subjected to a minimum drag. The land 68 is uniformly tapered whereby the drag decreases substantially uniformly from a maximum value at the first point 80 to a minimum value at the second point 82. The tubular segment 64 is illustrated in dash-dot outline in FIG. 2. Since the tubular segment 64 is subjected to a greater amount of drag at the first point 80 than at the second point 82, its rate of travel through the die means 26 will be less at the first point 80 than at the second point 82. Hence, the tubular segment 64 will bend about the first point 80 along a desired radius. As

the tubular segment 64 exits from the die means 26, it will engage the arcuate trough 32 of the forming guide means 28 to be guided thereby along the desired radius.

It will be noted in FIGS. 2 and 3, that the die means 26 not only causes the tubular segment 64 to be bent, but also causes a reduction in the outer diameter of the tubular segment 64. Since the circular shoulder 72 is offset from the elongated bore 24, the tubular segment 64 will be reduced by a greater amount at the first point 80 than it is at the second point 82. The reduction of the tubular segment 64 decreases substantially uniformly from the.

first point 80 to the second point 82 as evidenced by the showing in FIG. 3. In this embodiment, then, the drag is created by a reduction in the wall thickness of the tubular segment 64. However, the amount of reduction in the wall thickness varies from a maximum value at the first point 80 substantially uniformly to a minimum value at the second point 82. This differential reduction in the wall thickness compensates for the expected variation in the wall thickness of the formed elbow 62. This should be evident, since, in the shorter arc region wherein a thickening of the wall thickness is expected, a maximum amount of reduction is accomplished; and, in the longer arc region wherein a thinning of the wall thickness is expected, a minimum amount of reduction takes place.

Bending die means-alternwtive embodiments Alternative embodiments of the present die means are illustrated in FIGS. 4, 5 and 6, 7. Corresponding numerals will be employed to identify corresponding parts already described.

Referring now to FIGS. 4 and 5, there is illustrated a sizing die means 88 whose center corresponds with the center 76 of 'the elongated bore 24 and a bending die means 90 whose central axis is indicated at 92 in FIG. 5.

In FIG. 5, a vertical plane is illustrated by the dashdot line 94 which corresponds to the plane in which the cross-sectional view of FIG. 4 is taken.

The bending die means 90 comprises a tapered land 96 which in this embodiment is a surface in the form of a truncated right cylinder. The tapered land 96 includes an upper edge 98 which extends perpendicularly to the central axis 92 of the die means 90 and a lower edge 100 which is angled with respect to the central axis 92. Hence, the tapered land 96 provides axially extending lines of contact with the tubular segment 64 (shown in dash-dot outline) which vary in length from a maximum value at a first point 182 on its circumference to a minimum value at a diametrically opposite second oint 104 on its circumference. This relation is best shown in FIG. 4. Consequently, the tapered land 96 subjects the tubular segment 64 to a maximum frictional drag at the point 192 and to a minimum frictional drag at the point 104. The land 96 is uniformly tapered whereby the frictional drag decreases substantially uniformly from the maximum value at the first point 102 to the minimum value at the second point 104.

The sizing die means 88 also comprises a tapered land 106 which provides axially extending lines of contact with the tubular segment 64, whose lengths vary from a maximum value at a first point 108 in the plane 94, to substantially zero length at a second point 110 which is diametrically opposite to the first point 188. The tapered land 106 is created by offsetting the bending die means 90 with respect to the elongated bore 24, as can best be seen in FIG. 5. The ofisetting of the bending die means 91) and the elongated bore 24 provides the above-described differential reduction in the wall thickness of the tubular segment 64. The differential reduction in the wall thickness compensates for the normally expected variation in the wall thickness of the formed elbow member 62 (shown in dash-dot outline in FIG. 4). In this embodiment, then, the differential frictional drag provided by the bending die means 90 and the differential drag provided by reducing the wall thickness of the tubular segment 64 by the sizing die means 88 combine to subject the tubular segment 64 to a maximum amount of drag in one region of the die means 88, and to a minimum drag at a diametrically opposed region of the die means 88, 90. Consequently, the tubular segment 64 will bend about the region of maximum drag along a desired radius. The bent portion of the tubular segment 64 will, of course, engage the arcuate trough 32 of the forming guide means 28 and be guided thereby.

A further alternative embodiment of the present bending die means is illustrated in FIGS. 6 and 7. This embodiment will be employed for forming relatively large radius elbows wherein the variation in the wall thickness of the elbow is within the required tolerances. In this embodiment, the bending die means 90 is employed. Sizing die means 108 is provided having a uniform land 118 which is Combined tube forming and bending apparatus As stated above, the present invention contemplates the provision of apparatus which has the combined function of forming the tubular segments and then bending the same into the desired elbow members. Such apparatus is illustrated in FIG. 8 and indicated generally by the numeral 112. The tube forming and bending apparatus 112 comprises tube forming or first die means 114 and bending or second die means 116.

The first die means 114 comprises any conventional tube forming die means such as the frusto-conical land 118 illustrated in FIG. 8. The tube forming die means 114 is provided at the base of a billet receiving opening 120 formed in a block member 122. The tube forming and bending apparatus 112 includes a stern 124 having a mandrel 126 integral therewith and extending therebelow. The stem 124 and mandrel 126 are moved along a vertical axis into and out of the billet receiving opening 120, for example, by rneans'of the above-described stern operating means 36. The mandrel 126 and the first die means 114 cooperate to transform billets into tubular segments.

The bending or second die means 116 may comprise the above-described bending die means 26; or the sizing and bending die means 88, 90; or 110, 90.

The block member 122, the support block 22 and the forming guide means 28 are aligned and disposed in a suitable support means 128, the arrangement being such that the apparatus 112 is compact and may be operated continually, as will be described.

The tube forming and bending apparatus 112 is arranged to receive a billet 139; extrude the same through the tube forming die means 114 into a tubular segment 132 and thereafter force the tubular segment 132 through the bending die means 116 to form an elbow member. During each operation of the tube forming and bending apparatus 112, there is contained therein a billet 130, atubular seg--' the bending die means 116, the resulting elbow member 4 134 will have the required arc length.

As stated above, the billets 130 are extruded cold, i.e., at a temperature range of from about 100 F. to 175 R, which is well below the conventional temperature range of 800 F. to 1000 F. In order to reduce the amount of force required to extrude the cold billet 130, the billet is coated with a lubricant which preferably comprises a water insoluble metal soap. The billets may be prepared as follows:

Raw material, in the form of round bar stock, is subiected to a surface cleaning process such as sandblasting or the like. The cleaned bar is then cut or sheared to predetermined lengths to form the billets 148. The billets 148 are then cleaned by spraying or dipping them in a heated alkali solution to remove the remaining foreign matter from the surface. The billets are then rinsed in Water at a temperature of approximately 140 F., to remove the alkali.. From there, the billets are pickled in a sulfuric acid solution at a temperature of from about 140 F. to 180 F. either by spraying or dipping. After pickling, the billets are alternately rinsed in cold water and hot water (at approximately 160 F.) to remove all surface acid. The billets are then placed in a phosphate coating bath, at approximately 160 F. to 200 F., producing a zinc phosphate coating on the surfaces of the billets. The billets are again rinsed in cold water to remove any remaining acids or salts. The billets are then rinsed in a neutralizing medium, such as sodium nitrite, which is compatible with the lubricant to be used. The final step in the preparation of the billets is placing them in a reactive lubicant bath, such as sodium soap. The reactive lubricant bath is at a temperature of from 140 F. to 160 F. The lubricant bath causes a reaction wherein a water insoluble metal soap is formed. The billets are then pierced to provide them with an opening having the required inside diameter. The billets are now ready to be placed in the tube forming and bending apparatus 112. It should be noted at this point, that the particular neutralizing medium and reactive lubricant bath stated above are but one of many reagents which may react to provide a suitable lubricant coating and that they form no part of the present invention.

In FIG. 9, there is illustrated a billet 130 having a lubricant coating 136 provided on its surfaces.

Operation of apparatus 112 The operation of the tube forming and bending apparatus 112 will now be described with reference to FIGS.

IDA-10F.

In FIG. 10A, a first billet 130a is shown residing within the billet receiving opening 120 with the mandrel 126 and the stem 124 engaged therewith. The billet 130a is in position for extrusion through the tube forming die means 114.

At the completion of the first downward stroke of the stem 124 and the mandrel 126 as illustrated in FIG. 10B, the first billet 130a has been forced through the tube forming die means 114 so that a first tubular segment 132a is formed. Notice, however, that the first billet 130a has been incompletely extruded so that an unextruded upper end portion 138 thereof remains Within the tube forming die means 114.

As can be seen in FIG. 10C, the stem 124 and mandrel 126 have been withdrawn from the billet receiving opening 120 and a second billet 13% has been deposited therein. The second billet 13% is engaged with the extruded upper end portion 138 of the first billet 130a.

As illustrated in FIG. 10D, the stem 124 and mandrel 126 are lowered into engagement with the second billet 13% to force the same through the tube forming die means 114 so as to form a second tubular segment 13217; and so than an unextruded upper end portion 14% thereof remains within the tube forming die means 114. Simultaneous with the extrusion of the second billet 13% through the tube forming die means 114, the extrusion of the first billet 130a is completed and the first tubular segment 132a formed therefrom, is forced through the bending die means 116 so as to form a first elbow member 134a. Again, the first tubular segment 132a has been incompletely forced through the bending die means 116 so that an unbent upper end portion 142 remains Within the bending die means 116.

As can be seen in FIG. 10E, the stem 124 and mandrel 126 have been withdrawn from the billet receiving opening 120. A third billet 1300 is inserted into the billet receiving opening 120 into engagement with the unextruded upper end portion 140 of the second billet 13Gb. Thereafter, the stem 124 and mandrel 126 are lowered into engagement with the third billet 130a to displace the same through the tube forming die means 114.

As can be seen in FIG. 10F, the third billet 1300 is being extruded through the tube forming die means 114 to form a third tubular segment 1320. Simultaneously the second tubular segment 1321) is being forced through the bending die means 116 to form a second elbow member 13412. Simultaneously, the bending of the first tubular segment 132a has been completed and a formed elbow member 134a is discharged from the forming guide means 28.

Accordingly, the tube forming and bending apparatus 112 may be operated continually by inserting in one end a precoated, cold billet and withdrawing from its exit and a formed elbow member of a desired radius of curvature and arc length.

Although the invention has been shown in connection with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. In apparatus for bending cold tubular members, the combination comprising: a support block having an opening within which said tubular member is supported; die means at one end of said support block within said opening for causing said tubular member to bend along a desired radius, said die means comprising a tapered land whose axially extending lines of contact with said tubular member vary from a minimum length at a first point on said circumference to a maximum length at a second point on said circumference, said first and second points corresponding respectively to areas of maximum and minimum frictional drag; said tubular member bending about said first point during extrusion thereof; and means for forcibly moving said tubular member through said die means.

2. In apparatus for bending cold tubular members, the combination comprising: a support block having an opening within which said tubular member is supported; die means at one end of said support block within said opening for causing said tubular member to bend along a desired radius, said die means comprising a tapered land whose axially extending lines of contact with said tubular member vary from a maximum length at a first point on its circumference to a minimum length at a second point on its circumference, said first and second points corresponding respectively to areas of maximum and minimum frictional drag; said tubular member bending about said first point during extrusion thereof; and means for forcibly moving said tubular member through said die means.

3. The combination of claim 2 wherein said tapered land comprises a surface in the form of a truncated right circular cylinder.

4. In apparatus for bending cold tubular members, the combination comprising: a support block having an opening within which said tubular member is supported; a land disposed at one end of said support block and within said opening, said land comprising a surface in the form of a truncated oblique cone which provides drag between it and said tubular member on passage therethrough, said drag varying between a minimum value and a maximum value whereby said tubular member is caused to bend about the region of maximum drag along a desired radius; and means for forcibly moving said tubular member through said opening and over said land.

5. In apparatus for forming elbows by cold extrusion of pierced billets, comprising in combination: first die means for extruding a pierced billet into a tubular member; support means including an opening within which said tubular member is received for supporting the same during extrusion through said first die means; second die means disposed at the opposite end of said support means within said opening for causing said tubular member to bend along a desired radius, said die means comprising a tapered land engaged by said tubular member on passage therethrough, said tapered land providing a frictional drag between it and said tubular member which varies from a minimum value at a first point on its circu-mference to a maximum value at a second point on its circumference, said tubular member being bent about said first point; and means for forcibly moving said pierced billet through said first die means, said support means and said second die means.

6. The combination of claim wherein during an extrusion operation, said apparatus contains three of said billets, the first of said billets residing within said first die means in position for extrusion into said tubular member; the second of said billets having been extruded into a tubular member and residing within said support means; and the third of said billets having been extruded through said second die means and bent along the desired radius; the second of said billets being engaged at one end by the first of said billets and being engaged with the third of said billets at its other end; said means for forcibly moving said billets acting on the first of said billets for moving all of said billets through said apparatus.

7. The combination of claim 5 and including forming guide means disposed at the exit of said second die means for receiving the bent portion of said billet and for guiding same along the desired radius.

8. In apparatus for bending cold tubular members, the combination comprising: a support block having an elongated bore extending therethrough within which said tubular member resides and is supported; a radially inwardly extending shoulder disposed at one end of said bore and defining a die opening, said die opening having a diameter which is less than the diameter of said bore and whose center is offset from the central axis of said bore, said shoulder projecting inwardly at a maximum distance at a first point on its circumference and at a minimum distance at a diametrically opposed second point on its circumference whereby said tubular member is subjected to a maximum amount of frictional drag at said first point and to a minimum amount of frictional drag at said second point so that said tubular member bends at said first point along a desired radius; and means for moving said tubular member through said bore and said die opening.

9. A method of forming elbow members from cold tubular members, comprising the steps of (1) introducing a first of said tubular members into a support block; (2) forcibly moving the first of said tubular members partially through die means provided in said support block to incompletely extrude the same into an elbow shape of desired curvature, said die means subjecting said tubular member to frictional drag which varies from a maximum value at a first point on its circumference to a minimum value at a second opposed point on its circumference, the first of said tubular members bending about said first point; (3) introducing a second of said tubular members within said support block and into engagement with the unextruded end portion of the first of said tubular members; (4) forcibly moving the second and the first of said tubular members to complete the bending of the first of said tubular members and to incompletely extrude the second of said tubular members through said die means into an elbow shape of desired curvature; and (5) sequentially introducing additional ones of said tubular members within said support block and repeating step (4).

10. The method of bending cold pierced metal billets, comprising the steps of 1) coating the outer surfaces of a plurality of said billets with a lubricant; (2) forcibly moving one of said billets through a first die means extruding the same into a tubular member; and (3) sequentially forcibly moving said tubular member through a second die wherein said tubular member is subjected to a maximum fractional drag at a first point on its circumference and to a minimum frictional drag at a second point on its circumference whereby the extruded tubular member will bend about the said first point along a desired radius.

11. The method of continuously forming elbow members from cold pierced metal billets, comprising the steps of (1) coating the outer surfaces of a plurality of said billets with a lubricant material; (2) introducing a first of said billets within a first die means; (3) forcibly moving the first of said billets partially through said first die means to form a first tubular member; (4) introducing a second of said billets within said first die means into engagement with the unextruded end portion of the first of said billets; (5) forcibly moving the second of said billets partially through said first die means while simultaneously moving the first of said tubular members partially through a second die means which subjects said first tubular member to a frictional drag which varies from a maximum value at a first point on its circumference to a minimum value at a second diametrically opposed point on its circumference whereby said first tubular member is caused to bend about said first point along a desired radius; (6) introducing a third of said billets into said first die means into engagement with the unextruded end portion of the second of said billets; (7) forcibly moving the third of said billets partially through said die means while simultaneously moving the first tubular member completely through said second die means to complete its bending and moving said second tubular member through said first die means and partially through said second die means; and (8) sequentially introducing additional ones of said billets into said first die means, repeating step (7) and withdrawing completed elbow members from said second die means.

12. In apparatus for bending cold tubular members, the combination comprising: a support block having an opening in which said tubular member is supported; die means within said opening at one end of said support block for bending said tubular member along a desired radius, said die means comprising a tapered land engaged by said tubular member on passage therethrough, said tapered land providing a drag which varies from a minimum value at a first point on the circumference of said tubular member to a maximum value at a second point on the circumference of said tubular member, said tubular member being bent about said first point, and means for forcibly moving said tubular member through said die means, said tubular member being bent into an elbow-shaped member, the arc length of said elbowshaped member being determined by the initial length of said tubular member.

13. In apparatus for bending cold tubular members, the combination comprising: a support block having an opening in which said tubular member is supported; die means within said opening at one end of said support block for bending said tubular member along a desired radius, said die means comprising a tapered land engaged by said tubular member on passage therethrough, said tapered land providing a drag which varies from a minimum 1 1 l 2 value at a first point on the circumference of said tubular References Cited member to a maximum value at a second oint on the circumference of said tubular member, said tabular mem- UNITED STATES PATENTS her being bent about said first point, and means for forc- 1,891,333 12/1932 S ll 29 157 i'bly moving said tubular member through said die means, 5 2,750,026 6 /19 56 R d 72 467 X said tubular member being moved only partially through 2,76 ,742 10/1956 Lunfley 72 4 7 said die means, a second tubular member being intro- 2,976,908 3/ 1961 Ferguson 72.. 167

duced into said opening and engaged with the unextruded end portion of the first tubular member, said means for CHARLES LANHAM, primary Exmm-Mn forcibly moving the tubular member acting on said second 10 t b l b K. C. DECKER, Assistant Examiner. 

1. IN APPARATUS FOR BENDING COLD TUBULAR MEMBERS, THE COMBINATION COMPRISING: A SUPPORT BLOCK HAVING AN OPENING WITHIN WHICH SAID TUBULAR MEMBER IS SUPPORTED; DIE MEANS TO ONE END OF SAID SUPPORT BLOCK WITHIN SAID OPENING FOR CAUSING SAID TUBULAR MEMBER TO BEND ALONG A DESIRED RADIUS, SAID DIE MEANS COMPRISING A TAPERED LAND WHOSE AXIALLY EXTENDING LINES OF CONTACT WITH SAID TUBULAR MEMBER VARY FROM A MINIMUM LENGTH AT A FIRST POINT ON SAID CIRCUMFERENCE TO A MAXIMUM LENGTH AT A SECOND POINT ON SAID CIRCUMFERENCE, SAID FIRST AND SECOND POINTS CORRESPONDING RESPECTIVELY TO AREAS OF MAXIMUM AND MINIMUM FRICTIONAL DRAG; SAID TUBULAR MEMBER BENDING ABOUT SAID FIRST POINT DURING EXTRUSION THEREOF; AND MEANS FOR FORCIBLY MOVING SAID TUBULAR MEMBER THROUGH SAID DIE MEANS. 